The inventive concept relates to an apparatus and a method for drying a substrate, and more particularly, to an apparatus and a method for drying a substrate by using a supercritical fluid.
In general, a semiconductor device is formed through various processes, such as a photo process, an etching process, an ion implantation process, and a deposition process, on a substrate such as a silicon wafer. Further, in the processes, various foreign substances such as particles, organic contaminants, metal impurities are produced. Because the foreign substances cause defects and directly influence the performance and yield rate of the semiconductor device, the semiconductor manufacturing process is essentially accompanied by a cleaning process for removing the foreign substances.
The cleaning process includes a chemical processing process of removing contaminants from a substrate with a chemical, a wet cleaning process of removing the chemical residing on the substrate with pure water, and a drying process for drying the pure water residing on a surface of the substrate by supplying a drying fluid.
In the part, the drying process was performed by supplying heated nitrogen gas onto a substrate on which pure water is left. However, as the line width of a pattern formed on the substrate becomes smaller and the aspect ratio of the pattern becomes larger, pure water between patterns is not well removed. To achieve this, in recent years, pure water has been substituted on a substrate by a liquefied organic solvent, such as isopropyl alcohol, which is volatile and has a low surface tension as compared with pure water, and then a substrate has been dried by supplying heated nitrogen gas. However, because the organic solvent that is nonpolar and pure water that is polar are not easily mixed, a large amount of organic solvent should be supplied for a long time to substitute pure water with the liquefied organic solvent.
The conventional drying process has been performed in a method of substituting pure water on a substrate with an organic solvent, such as isopropyl alcohol, which has a relatively low surface tension.
However, because the drying method still causes a pattern collapse for a semiconductor having a fine circuit pattern having a line width of 30 nm or less even when an organic solvent is used, a supercritical drying process that overcomes the problems has recently replaced the existing drying processes.
When a substrate is dried by using a process fluid, the process fluid maintains a proper temperature when it is stored in a supply tank, but the temperature of the process fluid is lowered due to an adiabatic expansion. Accordingly, because the density of the process fluid increases and the surface tension thereof also increase, the process fluid influences the pattern on the substrate. Further, because the solubility for isopropyl alcohol becomes lower, the effect of removing isopropyl alcohol deteriorates.